FTIR imaging for the characterization of controlled-release drug delivery applications

Nicotine-magnesium aluminum silicate complexes processed by blending: Characterization for usage as drug carriers in mucoadhesive buccal discs

Complexation of nicotine (NCT) and magnesium aluminum silicate (MAS) has been formed in the dispersions that required multiple preparation steps. In this study, physical blending was used to produce NCT-MAS complexes. NCT, a free-base liquid state form, was adsorbed onto the MAS granules, where the diffusion and intercalation of NCT molecules into the MAS silicate layers occurred. These processes required a minimum of the 7-d-resting period to reach NCT complete distribution. FTIR, XRD, and 29Si NMR suggest that NCT could interact with MAS via hydrogen bonding, water bridging, and ionic electrostatic force. The 12 % NCT-MAS complexes enabled a sustained release of NCT, after a 2-min burst, in pH 6 phosphate buffer through a particle diffusion-controlled mechanism. Buccal discs formulated with NCT-MAS complexes and sodium alginate (SA) as drug carriers and matrix former could control NCT released through drug diffusion and swelling-controlled mechanisms. NCT release and membrane permeation increased with increasing NCT-MAS complexes or decreasing SA concentration. All NCT-MAS-containing buccal discs exhibited mucoadhesive properties related to the swelling characteristics of SA and MAS. Conclusively, NCT-MAS complexes can be produced through an uncomplicated single-step blending process, and the complexes obtained presented a potential to serve as drug carriers in buccal matrix formulations.

Generic Chemometric Models for Metabolite Concentration Prediction Based on Raman Spectra

Chemometric models for on-line process monitoring have become well established in pharmaceutical bioprocesses. The main drawback is the required calibration effort and the inflexibility regarding system or process changes. So, a recalibration is necessary whenever the process or the setup changes even slightly. With a large and diverse Raman dataset, however, it was possible to generate generic partial least squares regression models to reliably predict the concentrations of important metabolic compounds, such as glucose-, lactate-, and glutamine-indifferent CHO cell cultivations. The data for calibration were collected from various cell cultures from different sites in different companies using different Raman spectrophotometers. In testing, the developed “generic” models were capable of predicting the concentrations of said compounds from a dilution series in FMX-8 mod medium, as well as from an independent CHO cell culture. These spectra were taken with a completely different setup and with different Raman spectrometers, demonstrating the model flexibility. The prediction errors for the tests were mostly in an acceptable range (<10% relative error). This demonstrates that, under the right circumstances and by choosing the calibration data carefully, it is possible to create generic and reliable chemometric models that are transferrable from one process to another without recalibration.

Biomolecular and bioanalytical applications of infrared spectroscopy - A review

Infrared (IR; or mid-infrared, MIR; 4000-400 cm^-1; 2500-25,000 nm) spectroscopy has become one of the most powerful and versatile tools at the disposal of modern bioscience. Because of its high molecular specificity, applicability to wide variety of samples, rapid measurement and non-invasivity, IR spectroscopy forms a potent approach to elucidate qualitative and quantitative information from various kinds of biological material. For these reasons, it became an established bioanalytical technique with diverse applications. This work aims to be a comprehensive and critical review of the recent accomplishments in the field of biomolecular and bioanalytical IR spectroscopy. That progress is presented on a wider background, with fundamental characteristics, the basic principles of the technique outlined, and its scientific capability directly compared with other methods being used in similar fields (e.g. near-infrared, Raman, fluorescence). The article aims to present a complete examination of the topic, as it touches the background phenomena, instrumentation, spectra processing and data analytical methods, spectra interpretation and related information. To suit this goal, the article includes a tutorial information essential to obtain a thorough perspective of bio-related applications of the reviewed methodologies. The importance of the fundamental factors to the final performance and applicability of IR spectroscopy in various areas of bioscience is explained. This information is interpreted in critical way, with aim to gain deep understanding why IR spectroscopy finds extraordinarily intensive use in this remarkably diverse and dynamic field of research and utility. The major focus is placed on the diversity of the applications in which IR biospectroscopy has been established so far and those onto which it is expanding nowadays. This includes qualitative and quantitative analytical spectroscopy, spectral imaging, medical diagnosis, monitoring of biophysical processes, and studies of physicochemical properties and dynamics of biomolecules. The application potential of IR spectroscopy in light of the current accomplishments and the future prospects is critically evaluated and its significance in the progress of bioscience is comprehensively presented.

Applications of Fourier transform infrared spectroscopy to pharmaceutical preparations

Introduction: Various pharmaceutical preparations are widely used for clinical treatment. Elucidation of the mechanisms of drug release and evaluation of drug efficacy in biological samples are important in drug design and drug quality control.Areas covered: This review classifies recent applications of Fourier transform infrared (FTIR) spectroscopy in the field of medicine to comprehend drug release and diffusion. Drug release is affected by many factors of preparations, such as drug delivery system and microstructure polymorphism. The applications of FTIR imaging and nano-FTIR technique in biological samples lay a foundation for studying drug mechanism in vivo.Expert opinion: FTIR spectroscopy meets the research needs on preparations to understand the processes and mechanisms underlying drug release. The combination of attenuated total reflectance-FTIR imaging and nano-FTIR accompanied by chemometrics is a potent tool to overcome the deficiency of conventional infrared detection. FTIR shows an enormous potential in drug characterization, drug quality control, and bio-sample detection.

Preparation, characterization, and pharmacokinetics in swine of a florfenicol enteric formulation prepared using hot-melt extrusion technology

The objective of this work was to manufacture an enteric formulation of florfenicol (FF) using hot-melt extrusion (HME) technology and to evaluate its in vitro dissolution and in vivo pharmacokinetics. For the HME process, hypromellose acetate succinate LG (HPMCAS-LG) was the enteric polymer mixed with FF, and the two components were extruded with a standard screw configuration at a speed of 50 rpm. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and Fourier transform infrared spectroscopy (FT-IR) were performed to characterize the HME extrudate. The release percentage of the enteric formulation in the acidic stage was <10% of the loaded FF, whereas that in the phosphate buffer stage was >80%. Pharmacokinetic evaluations in swine revealed that the enteric formulation had a longer t_1/2λ and MRT than commercially available FF powder (FULAIKA^® ), indicating that the novel formulation exhibited enteric and sustained release properties. Compared with the commercial product, the relative bioavailability of the enteric formulation reached up to 117.2%. This study suggests that this formulation may have potential for future commercialization.

Fourier transform infrared imaging spectroscopy of the diffusion process of D2O into polyamide 11

Fourier transform infrared (FT-IR) spectroscopic imaging with focal plane array detectors has proved a powerful technique for rapid chemical visualization of samples, with a lateral resolution up to 10-15 microm in the transmission micro mode. In the present communication the application of this technique is described for the study of the diffusion of D2O into a polyamide 11 (PA11) film. Apart from the in situ visualization of the diffusion front propagation in the time-resolved FT-IR images, the type of diffusion and the diffusion coefficient of D2O in the investigated polyamide have been determined.

Quantitative determination of pharmaceutical drug formulations by near-infrared spectroscopic imaging

Over the last decade Fourier transform infrared (FT-IR) and near-infrared (NIR) spectroscopic imaging with focal plane array (FPA) detectors have proved powerful techniques for the rapid visualization of samples by a combination of spectroscopic and spatial information. Using these methods, selected sample areas can be analyzed with reference to the identification and localization of chemical species by FT-IR spectroscopy in the transmission or attenuated total reflection (ATR) mode and by NIR spectroscopy in diffuse reflection with a lateral resolution in the micrometer range. The present communication focuses on the quantitative determination of the active ingredient composition of a solid drug formulation by NIR spectroscopic imaging with a focal plane array detector and the results obtained are compared to the quantitative data obtained by conservative light-fiber NIR spectroscopic diffuse reflection measurements with a single-element detector. The communication also addresses the issue of penetration depth of NIR radiation into the investigated solid material.

Pharmaceutical applications of vibrational chemical imaging and chemometrics: a review

The emergence of chemical imaging (CI) has gifted spectroscopy an additional dimension. Chemical imaging systems complement chemical identification by acquiring spatially located spectra that enable visualization of chemical compound distributions. Such techniques are highly relevant to pharmaceutics in that the distribution of excipients and active pharmaceutical ingredient informs not only a product's behavior during manufacture but also its physical attributes (dissolution properties, stability, etc.). The rapid image acquisition made possible by the emergence of focal plane array detectors, combined with publication of the Food and Drug Administration guidelines for process analytical technology in 2001, has heightened interest in the pharmaceutical applications of CI, notably as a tool for enhancing drug quality and understanding process. Papers on the pharmaceutical applications of CI have been appearing in steadily increasing numbers since 2000. The aim of the present paper is to give an overview of infrared, near-infrared and Raman imaging in pharmaceutics. Sections 2 and 3 deal with the theory, device set-ups, mode of acquisition and processing techniques used to extract information of interest. Section 4 addresses the pharmaceutical applications.

Penetration kinetics of dimethyl sulphoxide and glycerol in dynamic optical clearing of porcine skin tissue in vitro studied by Fourier transform infrared spectroscopic imaging

By use of a Fourier transform infrared (FTIR) spectroscopic imaging technique, we examine the dynamic optical clearing processes occurring in hyperosmotically biocompatible agents penetrating into skin tissue in vitro. The sequential collection of images in a time series provides an opportunity to assess penetration kinetics of dimethyl sulphoxide (DMSO) and glycerol beneath the surface of skin tissue over time. From 2-D IR spectroscopic images and 3-D false color diagrams, we show that glycerol takes at least 30 min to finally penetrate the layer of epidermis, while DMSO can be detected in epidermis after only 4 min of being topically applied over stratum corneum sides of porcine skin. The results demonstrate the potential of a FTIR spectroscopic imaging technique as an analytical tool for the study of dynamic optical clearing effects when the bio-tissue is impregnated by hyperosmotically biocompatible agents such as glycerol and DMSO.

Simultaneous FTIR spectroscopic imaging and visible photography to monitor tablet dissolution and drug release

PURPOSE

Previous studies of hydroxypropyl methylcellulose (HPMC)-based tablet during exposure to water showed a number of 'fronts' moving into the tablet but led to contradictory interpretations. These fronts are related to water penetration into and dissolution of the tablet, but the exact nature can not be derived from visible photographic evidence. A method to study tablet dissolution simultaneously by Fourier transform infrared-attenuated total reflection (FTIR-ATR) imaging and macro-photography can assist in providing correct interpretation of the observed fronts.

METHODS

Therefore, the combination of macro-photography and FTIR-ATR spectroscopic imaging was developed and used to interpret the physical changes leading to the observed fronts. Buflomedyl pyridoxal phosphate (BPP), a coloured drug, was used as a model drug.

RESULTS

The quantitative results obtained by FTIR-ATR imaging enabled the attribution of the three observed fronts (inside to outside) to: (1) true water penetration, possibly combined with (partial) dissolution of buflomedyl pyridoxal phosphate (BPP); (2) total gellification of HPMC; (3) erosion front.

CONCLUSIONS

The method to study dissolution of a tablet simultaneously by FTIR-ATR imaging and macro-photography has been developed and used to obtain reliable interpretation of the fronts observed during tablet dissolution.

Chemical imaging of the stratum corneum under controlled humidity with the attenuated total reflection Fourier transform infrared spectroscopy method

Attenuated total reflection Fourier transform infrared spectroscopic imaging was applied to study human stratum corneum (SC) tissue, the outermost layer of the skin. This imaging approach was combined with a controlled environment cell to demonstrate the possibility of obtaining chemical images of SC exposed to a wide range of relative humidities and diffusion of ethanol through the SC tissue with a specially designed liquid cell. The effect of water vapor sorbed into the SC on the distribution of other components in the SC was studied. Principal component analysis was applied in conjunction with univariate analysis to differentiate the distribution of different components in the SC. Swelling of the SC, a heterogeneous distribution of natural moisturizing factor and water, was detected upon the increase of relative humidity. The approach to image the penetration of liquid ethanol into the SC was also demonstrated and showed good potential and implications for studying transdermal drug delivery.

Infrared Spectroscopic Imaging for Noninvasive Detection of Latent Fingerprints

The capability of Fourier transform infrared (FTIR) spectroscopic imaging to provide detailed images of unprocessed latent fingerprints while also preserving important trace evidence is demonstrated. Unprocessed fingerprints were developed on various porous and nonporous substrates. Data-processing methods used to extract the latent fingerprint ridge pattern from the background material included basic infrared spectroscopic band intensities, addition and subtraction of band intensity measurements, principal components analysis (PCA) and calculation of second derivative band intensities, as well as combinations of these various techniques. Additionally, trace evidence within the fingerprints was recovered and identified.

Combined Fourier-transform infrared imaging and desorption electrospray-ionization linear ion-trap mass spectrometry for analysis of counterfeit antimalarial tablets

This paper reports use of a combination of Fourier-transform infrared (FTIR) spectroscopic imaging and desorption electrospray ionization linear ion-trap mass spectrometry (DESI MS) for characterization of counterfeit pharmaceutical tablets. The counterfeit artesunate antimalarial tablets were analyzed by both techniques. The results obtained revealed the ability of FTIR imaging in non-destructive micro-attenuated total reflection (ATR) mode to detect the distribution of all components in the tablet, the identities of which were confirmed by DESI MS. Chemical images of the tablets were obtained with high spatial resolution. The FTIR spectroscopic imaging method affords inherent chemical specificity with rapid acquisition of data. DESI MS enables high-sensitivity detection of trace organic compounds. Combination of these two orthogonal surface-characterization methods has great potential for detection and analysis of counterfeit tablets in the open air and without sample preparation.

Controlled release of 5-fluorouridine from radiation-crosslinked poly(ethylene-co-vinyl acetate) films

The effect of gamma-radiation doses of 12.5-380 kGy on the infrared spectra, gel content, mechanical properties, and the release of oxobutyl-5-fluoro-2'-deoxyuridine (OfdUrd, an antitumor agent) from poly(ethylene-co-vinyl acetate) (EVA) films was studied. The results showed that the application of radiation doses produced a crosslinking reaction leading to a maximum gel content of about 85% in the case of 150 kGy. Higher doses did not increase the gel content in EVA films. The mechanical properties (tensile strength, percentage elongation at break and Young's modulus) of all studied EVA matrices were affected by the exposure to gamma-radiation. Irradiation doses over 50 kGy caused an increase in the Young's modulus of EVA and at the same time a decrease in the strain per cent. Moreover, the network structure formed after irradiation reduced significantly the OFdUrd release from EVA films. In this manner, the radiation dose applied to the polymeric matrix modulated the release of OFdUrd, avoiding the high concentrations that may cause severe systemic toxicity. The loading of OFdUrd to EVA film triggered a slight hyperemia after implantation, while the inflammatory reaction was only observed during the first two days.

Regions of interest in FTIR imaging applications: Diffusion of nicotine into ethylene-co-vinyl acetate films

Effective image analysis of dynamic processes, such as diffusion and dissolution, requires precise reporting of component locations in space and time. An improved method for analyzing FTIR images is described which employs hypothesis testing in the spatial and temporal domains. Changes in the observed absorbance (over space and time) are revealed by comparison to a reference statistic, which can be tailored by choosing the size of a region of interest. This improved analysis method was used to compare the rates of diffusion of nicotine into poly(ethylene-co-vinyl acetate) film from aqueous solutions containing anionic and nonionic surfactants. Compared to a solution without surfactant, sodium dodecyl sulfate inhibited the uptake of nicotine from aqueous solution whereas Tween 40 enhanced the uptake. The nicotine diffusion rate also showed a dependence on the length of the hydrophobic segment of nonionic surfactants. These results demonstrate the roles of solubilization, wetting, and viscosity on diffusion-controlled drug release.

Pharmaceutical applications of Mid-IR and Raman spectroscopy

Mid-IR and Raman spectroscopy are versatile tools in pharmaceutics and biopharmaceutics, with a wide field of applications ranging from characterization of drug formulations to elucidation of kinetic processes in drug delivery. After an introduction to the basic principles of IR and Raman spectroscopy, new developments in applications of these methods for studying drug delivery systems, in particular topical drug delivery, will be reviewed. FTIR-ATR is a well-established standard method used to study drug release in semisolid formulations, drug penetration, and influence of penetration modifiers; it is also capable of in vivo studies. FTIR-PAS has been applied to measure drug content in semisolid and solid formulations, to determine drug penetration into artificial and biological membranes. The big advantage of this technique is the possibility of spectral depth profiling. However, FTIR-PAS is so far limited to in vitro investigations. Raman spectroscopy can be used to characterize the structure of colloidal drug carrier systems. Raman spectroscopy is readily applicable to in vivo studies, but such investigations must fulfill the relevant laser safety guideline. Recently, there has been tremendous technical improvement in vibrational microspectroscopy. FTIR imaging shows great promise in its ability to visualize the drug and excipient distribution in pharmaceutical formulations such as tablets and therapeutic transdermal systems, as well as to reveal the mechanism of drug release. Furthermore, this unique technique offers completely new possibilities to study the lateral diffusion of drugs.

Fourier transform infrared imaging of stereoregular poly(methyl methacrylate) dissolution

Fourier transform infrared (FT-IR) imaging was used to study dissolution of stereoregular poly(methyl methacrylate) (PMMA) films in toluene, benzene, chloroform, acetic acid, and 2-ethoxyethanol. Images of the polymer-solvent interface showed that syndiotactic (sPMMA), atactic (aPMMA), and isotactic (iPMMA) samples dissolved in acetic acid and chloroform; only iPMMA dissolved in benzene, toluene, and 2-ethoxyethanol. Concentration profiles allowed quantitative comparison of each polymer-solvent system. In the cases of chloroform and acetic acid, the rate of polymer dissolution increased with increasing isotacticity. Dissolution of PMMA in chloroform was observed to coincide with development of strong polymer-solvent interactions. The results of systems containing toluene, benzene, and 2-ethoxyethanol reflect kinetic effects on dissolution, including solvent size and stiffness of the polymer backbone.

The use of FT-IR imaging as an analytical tool for the characterization of drug delivery systems

FT-IR imaging spectroscopy is well suited for studying dynamic processes occurring in multi-component systems. Each component is resolved spatially based on the spectral response at each detector element. Additionally, the sequential collection of images tracks the movement of each component over time. In this study, the delivery characteristics of the drug, testosterone, suspended in a poly(ethylene oxide) (PEO) matrix was observed using this technique. Drug release occurred as the hydrophilic, erodible polymer underwent controlled dissolution, exposing the drug to the aqueous environment. The subsequent conversion of the drug into the therapeutic aqueous form completed the delivery process. Qualitative evaluation of the false color composite infrared images led to the elucidation of two distinct delivery mechanisms, dependent on the degree of drug loading. The spatially embedded spectral features led to the quantification of the drug release rates as well as the rates of polymer dissolution. The rates for both polymer dissolution and drug release were evaluated using well-established models. Additionally, the homogeneity of the drug dispersion for different loadings was characterized. The roles of chemical interactions across the solvent interface of species were also investigated. Changes in each component from the bulk to the solvated region were investigated, revealing changes in concentration and polymer orientation as well as inter-species interactions.